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Abstract:

A multiple reservoir or chambered implantable pumps is disclosed. The
pump according to the present invention is particularly useful in
allowing for multiple constant flow rates to be provided from an
otherwise constant flow implantable pump. The pump is also useful in
allowing for housing of multiple active substances. A multiple reservoir
implantable pump is also disclosed, which has at least one chamber
capable of providing a constant flow rate and at least one chamber
capable of being utilized for patient controlled injections. Methods of
providing active substances to patients utilizing such pumps are also
disclosed.

Claims:

1. A method of providing different constant flow rates of an active
substance to a patient comprising the steps of: providing an implantable
device having at least first and second active substance chambers; and
filling at least one of said first and second chambers or both of said
chambers with said active substance in order to provide a selected flow
rate of said active substance to said patient, wherein filling only said
first chamber with said active substance provides a first flow rate of
said active substance, filling only said second chamber with said active
substance provides a second flow rate of said active substance, and
filling both said first and second chambers with said active substance
provides a third flow rate of said active substance.

2. The method according to claim 1, wherein said implantable device
further includes an outlet in fluid communication with said active
substance chambers.

3. The method according to claim 2, wherein said implantable device
further includes a first resistor in fluid communication between said
first chamber and said outlet, and a second resistor in fluid
communication between said second chamber and said outlet.

4. The method according to claim 1, wherein said filling step includes
utilizing a syringe to pierce a septum located over a replenishment
opening associated with one of said first or second active substance
chambers.

5. The method according to claim 1, further comprising the step of
filling a bolus port with said active substance to directly apply said
active substance to said patient.

6. The method according to claim 1, wherein said first and second
chambers are filled with the same active substance.

7. The method according to claim 1, wherein said first and second
chambers are capable of being filled with different active substances.

8. The method according to claim 1, wherein said filling step includes
filling said first and second active substance chambers with two
different active substances.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. application Ser. No.
11/137,284 and a divisional of U.S. application Ser. No. 11/136,771, both
filed on May 25, 2005, the disclosures of which are incorporated herein
by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to implantable devices, and more
particularly to a multiple reservoir implantable pump that may be
designed to allow different constant flow rates and bolus injection
capability.

[0003] Implantable pumps have been well known and widely utilized for many
years. Typically, pumps of this type are implanted into patients who
require the delivery of active substances or medication fluids to
specific areas of their body. For example, patients that are experiencing
severe pain may require painkillers daily or multiple times per day.
Absent the use of an implantable pump or the like, a patient of this type
would be subjected to one or more painful injections of such medication
fluids. In the case of pain associated with more remote areas of the
body, such as the spine, these injections may be extremely difficult to
administer and particularly painful for the patient. Furthermore,
attempting to treat conditions such as this through oral or intravascular
administration of medication often requires higher doses of medication
and may cause severe side effects. Therefore, it is widely recognized
that utilizing an implantable pump may be beneficial to both a patient
and the treating physician.

[0004] Many implantable pump designs have been proposed. For example, U.S.
Pat. No. 4,969,873 ("the '873 patent"), the disclosure of which is hereby
incorporated by reference herein, teaches one such design. The '873 is an
example of a constant flow pump, which typically include a housing having
two chambers, a first chamber for holding the specific medication fluid
to be administered and a second chamber for holding a propellant. A
flexible membrane may separate the two chambers such that expansion of
the propellant in the second chamber pushes the medication fluid out of
the first chamber. This type of pump also typically includes an outlet
opening connected to a catheter for directing the medication fluid to the
desired area of the body, a replenishment opening for allowing for
refilling of medication fluid into the first chamber and a bolus opening
for allowing the direct introduction of a substance through the catheter
without introduction into the first chamber. Both the replenishment
opening and the bolus opening are typically covered by a septum that
allows a needle or similar device to be passed through it, but properly
seals the openings upon removal of the needle. As pumps of this type
provide a constant flow of medication fluid to the specific area of the
body, they must be refilled periodically with a proper concentration of
medication fluid suited for extended release.

[0005] Implantable pumps may also be of the programmable type. Pumps of
this type provide variable flow rates, typically through the use of a
solenoid pump or a peristaltic pump. In the solenoid pump, the flow rate
of medication fluid can be controlled by changing the stroke rate of the
pump. In the peristaltic pump, the flow rate can be controlled by
changing the roller velocity of the pump. However, both of these types of
programmable pumps require intricate designs and complicated controlling
mechanisms. As such, it is more desirable to utilize pumps having designs
similar to the aforementioned constant flow pumps.

[0006] Nonetheless, the benefit of providing a variable flow rate pump, or
at least a pump having the capability of multiple fixed flow rates,
cannot be forgotten. While a constant flow of medication such as a
painkiller may indeed be useful in dulling chronic pain, there may be
times when a patient may require additional pain relief. With a constant
flow pump, the flow rate is fixed, so the physician or medical
professional may only provide such relief by direct injections of
painkillers and the like through the aforementioned bolus port (which
provides direct access to the afflicted area), or by increasing the
overall active substance concentration of the fluid housed in the pump.
While indeed useful, the former amounts to nothing more than additional
injections, something the pump is designed to circumvent. In addition,
the latter may be considered less convenient for the physician or medical
professional, since it requires choosing a different concentration of
medicine, rather than merely adjusting the flow rate of the already
present medication via an external programmer, as would be done with a
programmable pump.

[0007] In addition, pumps are known that normally act in a fashion similar
to the aforementioned constant flow type pumps, but that also allow for a
patient controlled bolus dose. These pump types are sometimes referred to
as Patient Controlled Actuation ("PCA") pumps. One example of such a pump
is disclosed in U.S. Pat. No. 6,283,944, the disclosure of which is
hereby incorporated by reference herein. During periods of regular pain
or the like, PCA pumps provide a constant flow rate of medication fluid
to a patient. However, during periods of heightened pain, a PCA pump may
be actuated by a patient to provide an additional medication injection.
Essentially, this allows for a bolus injection, in line with that
described above, without the need for the use of a needle or syringe. PCA
pumps also typically include a safety mechanism for preventing a patient
from overdosing themselves. While such designs may be beneficial in light
of standard constant flow type implantable pumps, nevertheless, such
designs are often complicated and bulky.

[0008] Therefore, there exists a need for an implantable constant flow
pump, which allows for multiple fixed flow rates and may be configured to
allow for patient controlled bolus doses or the like.

BRIEF SUMMARY OF THE INVENTION

[0009] A first aspect of the present invention is an implantable device
for dispensing an active substance to a patient. A first embodiment of
this first aspect includes a propellant chamber defined by a first
flexible membrane and a second flexible membrane, a first active
substance chamber separated from the propellant chamber by the first
flexible membrane, and a second active substance chamber separated from
the propellant chamber by the second flexible membrane. The implantable
device may further include an outlet in fluid communication with the
first and second active substance chambers, and a resistor in
communication between each of the chambers and the outlet. The
implantable device may also include first and second replenishment
openings for refilling the first and second chambers. These openings may
be offset from the chambers so as to allow for the height of the device
to be reduced. The implantable device is preferably capable of housing
two different active substances in the chambers.

[0010] A second embodiment of this first aspect is an implantable pump.
The implantable pump of this embodiment includes a housing defining at
least three chambers and an outlet in fluid communication with at least
two of the chambers. One of the chambers is juxtaposed between two
flexible membranes and contains a propellant capable of expanding
isobarically.

[0011] A second aspect of the present invention is a method of providing
different constant flow rates of an active substance to a patient. The
method in accordance with this second aspect includes the steps of
providing an implantable device having at least first and second active
substance chambers and filling at least one of the first and second
chambers or both of the chambers with the active substance in order to
provide a selected flow rate of the active substance to the patient.
Filling only the first chamber with the active substance preferably
provides a first flow rate of the active substance, filling only the
second chamber with the active substance preferably provides a second
flow rate of the active substance, and filling both the first and second
chambers with the active substance preferably provides a third flow rate
of the active substance.

[0012] A third aspect of the present invention is an implantable pump with
patient controlled actuation capabilities. The pump in accordance with
this third aspect preferably includes a housing defining at least a
first, second and third chamber, an outlet in fluid communication with
the first chamber, and a patient controlled actuation mechanism in fluid
communication with the second chamber. The third chamber is preferably
juxtaposed between two flexible membranes. The third chamber may house a
propellant capable of expanding isobarically, thereby causing fluid
contained within the first and second chambers to be dispelled therefrom.
The patient controlled actuation mechanism includes a valve assembly is
preferably capable of being actuated by the patient, where selective
operation of the valve assembly is accomplished by one or more magnets.
The valve assembly may further include a first cylinder housing a first
piston, and a second cylinder housing a second piston, where displacement
of the first piston causes actuation of a dose of an active substance to
a patient. The pump may also include means for selectively actuating the
one or more magnets and means for preventing over medication of a patient

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more complete appreciation of the subject matter of the present
invention and the various advantages thereof can be realized by reference
to the following detailed description in which reference is made to the
accompanying drawings in which:

[0014] FIG. 1 is a cross sectional front view of an implantable pump in
accordance with an embodiment of the present invention.

[0015] FIG. 2 is a top view of the implantable pump shown in FIG. 1.

[0016]FIG. 3 is an enlarged view of an attachment area of the pump shown
in FIG. 1.

[0017] FIG. 4 is a cross sectional front view of an implantable pump in
accordance with another embodiment of the present invention.

[0019] FIG. 6 is a cross sectional left side view of the implantable pump
shown in FIG. 4, showing a valve assembly therein.

[0020] FIG. 7 is an enlarged cross section view of the valve assembly
shown in FIG. 5, in a first position.

[0021] FIG. 8 is an enlarged cross section view of the valve assembly
shown in FIG. 5, in a second position.

[0022] FIG. 9 is an enlarged cross section view of the valve assembly
shown in FIG. 5, in a third position.

[0023] FIG. 10 is an enlarged cross section view of the valve assembly
shown in FIG. 5, in a fourth position.

DETAILED DESCRIPTION

[0024] In describing the preferred embodiments of the subject matter
illustrated and to be described with respect to the drawings, specific
terminology will be used for the sake of clarity. However, the invention
is not intended to be limited to any specific terms used herein, and it
is to be understood that each specific term includes all technical
equivalents which operate in a similar manner to accomplish a similar
purpose.

[0025] Referring to the drawings, wherein like reference numerals refer to
like elements, there is shown in FIGS. 1 and 2, in accordance with
various embodiments of the present invention, an implantable pump
designated generally by reference numeral 10. In a preferred embodiment,
pump 10 is a constant flow pump including a housing 12, which defines an
interior having three reservoirs or chambers 14, 16 and 18. As best shown
in FIG. 1, chamber 18 is preferably formed between two flexible membranes
20 and 22, while chamber 14 is formed between a top portion 12a of
housing 12 and membrane 20, and chamber 16 is formed between a bottom
portion 12b of housing 12 and membrane 22. It is noted that flexible
membranes 20 and 22 may be of any design known in the art, for example, a
membrane like that disclosed in commonly owned U.S. Pat. No. 5,814,019,
the disclosure of which is hereby incorporated by reference herein. In a
preferred embodiment, chambers 14 and 16 are designed and configured to
receive and house active substances such as medication fluids for the
relief of pain, treatment of spasticity and neuro-mechanical deficiencies
and the administration of chemotherapy, while chamber 18 is preferably
designed and configured to contain a propellant which expands
isobarically under constant body heat. This expansion necessarily
displaces membranes 20 and 22, towards top portion 12a and bottom portion
12b respectively, so as to expel any active substances contained within
chambers 14 and 16. This will be discussed more fully below.

[0026] Pump 10 further includes a first replenishment port 24 formed in
housing 12. Essentially, first replenishment port 24 is an opening formed
in both top portion 12a and bottom portion 12b of housing 12. This port
is preferably covered by a first septum 26, which is capable of being
pierced by an injection needle and, upon removal of such needle, is
capable of automatically resealing itself. Septa of this type are well
known to those of ordinary skill in the art. As pump 10 is designed to
medicate a patient over a limited period of time, first replenishment
port 24 is utilized for replenishing chamber 16 when empty or near empty.
As shown in FIG. 1, port 24 is connected to chamber 16 by a first passage
28. In addition, housing 12 preferably includes a second, replenishment
port 30 for replenishing chamber 14 with an active substance or the like,
through the connection formed by second passage 34. Similar to first
replenishment port 24, second replenishment port 30 is covered by a
second, septum 32. However, as shown in FIGS. 1 and 2, port 30 and septum
32 are ring shaped, so that they extend around port 24. This design
allows for both replenishment ports to be located in a relatively small
area without requiring the need for a larger housing 12.

[0027] During a replenishment procedure, a physician and/or other medical
professional typically inserts an injection needle into an area of a
patient's body where pump 10 is located, such that it may pierce one of
first septum 26 or second septum 32. Thereafter, operation of the needle
causes injection of solution from the needle to pass into either chamber
14 through passage 34 or chamber 16 through passage 28. It is noted that
the particular dimension of pump 10 and/or the patient's need may require
such a process to be repeated at given intervals, for example, monthly,
weekly, etc. In addition, as will be more fully discussed below, the
replenishment process may be performed so as to vary the particular flow
rate of a medication fluid to the patient. Pump 10, as shown in FIG. 1,
also includes an outlet catheter 36 for remote delivery of a fluid
contained within chambers 14 or 16 to a specific location within the body
of a patient. Catheter 36 may be any well known catheter suitable for
directing a medication fluid or the like to a location away from pump 10.
For example, catheter 36 may direct medication fluid from a pump
implanted at or near the surface of a patient's body to the spinal or
other remote area. In the embodiment shown in FIG. 1, catheter 36 is in
fluid communication with both chambers 14 and 16 through a series of
connected passages. Specifically a first flow resistor 38 is connected to
chamber 14, while a second flow resistor 40 is connected to chamber 16.
It is noted that both resistors 38 and 40 may be any fluid resistor known
in the art. In their most simplistic form, resistors 38 and 40 are
essentially narrow tubes or capillaries which are dimensioned so as to
allow a maximum flow rate therethrough. Thus, regardless of the flow rate
of fluid from either chamber 14 or 16, resistors 38 and 40 act as
restrictors and govern the maximum rate. Resistors 38 and 40 are
preferably connected to a collecting duct 42, which is in turn connected
to a tube or capillary 44 in communication with catheter 36.

[0028] In operation, expansion of propellant housed within chamber 18
exerts a force upon membranes 20 and 22. This force displaces membranes
20 and 22, towards top portion 12a and bottom portion 12b respectively,
which in turn necessarily expels fluid contained in chambers 14 and 16
through resistors 38 and 40 respectively and ultimately out catheter 36.
The flow rate which was determined by resistors 38 and 40 determines the
flow rate of the fluid through and out of catheter 36.

[0029] In addition to the aforementioned first and second replenishment
ports 24 and 30, pump 10 also preferably includes a bolus port 46 covered
by a bolus septum 48. Essentially, this bolus port allows for direct
introduction of a solution into outlet catheter 36 and to the specific
target area of the body. This port is particularly useful when a patient
requires additional or stronger medication, such as a single bolus
injection, and/or when it is desired to test the flow path of catheter
36. Such an injection is performed in a similar fashion to the above
discussed injection in replenishment ports 24 and 30. As shown in FIG. 1,
fluid injected into bolus port 46 passes through bolus passage 50 and
into collecting duct 42. Thereafter, similar to above, such fluid passes
through tube 44 and out catheter 36. Thus, an injection into bolus port
46 bypasses resistors 38 and 40, and thus provides direct access to
catheter 36, without any reduction in flow rate. It is also possible to
utilize bolus port 46 to withdraw fluid from the body. For example, where
pump 10 is situated within the body such that catheter 36 extends to the
vertebral portion of the spinal column, a needle with a syringe connected
thereto may be inserted into bolus port 46 and operated to pull spinal
fluid through catheter 3 and into the syringe.

[0030] The design of pump 10 preferably allows for the selective
administration of any fluid housed therein, at up to three different flow
rates. As discussed above, upon the expansion of a propellant housed
within chamber 18, any fluid housed within chambers 14 and 16 is
ultimately expelled through catheter 36. The aforementioned resistors 38
and 40 dictate the maximum flow rate for any fluid being expelled from
chambers 14 and 16 respectively. In certain preferred embodiments, these
resistors differ in the maximum flow rate for which they allow. Thus,
depending upon which chamber(s) is filled/injected with fluid, the flow
rate through catheter 36 will preferably vary. For example, if chamber 14
is filled with a fluid, and chamber 16 is empty, the overall flow rate of
fluid from pump 10 is determined by resistor 38. Alternatively, if
chamber 16 is filled with a fluid, and chamber 14 is empty, the overall
flow rate of fluid from pump 10 is determined by resistor 40. If both
chambers 14 and 16 are filled with a fluid, the highest flow rate occurs
and is determined by the combination of the flow rates dictated by
resistors 38 and 40. Clearly, this three flow rate capability is
beneficial in varying the flow rate of a medication fluid or the like
depending upon the particular needs of a patient.

[0031] It is noted that regardless of the amount of fluid being housed in
either chambers 14 or 16, or both, the pressure being exerted on
membranes 20 and 22 by expanding propellant housed in chamber 18 is
sufficient for expelling the fluid therefrom. Thus, pump 10 is designed
so that propellant contained in chamber 18 expands and exerts a force
strong enough to always push fluid from chambers 14 and 16. In turn,
resistors 38 and 40 are designed to reduce this initial flow rate from
chambers 14 and 16, so that regardless of the force being applied to
membranes 20 and 22, by the propellant, a constant flow rate of fluid
into collection duct 42 may be seen. In other words, pump 10 is designed
so that the minimum flow rate of fluid directly from chambers 14 and 16
should always be greater than the flow rate of the same fluid through
resistors 38 and 40. This ensures that a predetermined constant flow of
fluid will occur regardless of the overall amount of fluid contained in
chambers 14 and 16.

[0032] In operation, a doctor and/or other medical professional may easily
utilize pump 10 so as to provide three different flow rates of medication
to a patient. Initially, pump 10 may be implanted into the body of a
patient by well known methods for implanting such implantable devices. As
shown in FIG. 2, suture holes 52 may be useful in attaching pump 10 to a
specific portion of the body so that catheter may be directed to the
portion which requires the medication fluid or the like. In certain
preferred embodiments, pump 10 includes four suture holes 52 that each
extend through housing 12 from top portion 12a to bottom portion 12b, and
that may be utilized in conjunction with sutures or the like. Once pump
10 is implanted in the body of a patient, the aforementioned medical
professional may essentially pick and choose which chambers to fill. As
set forth above, filling of either chamber 14 or chamber 16 may provide
either a first or second flow rate of fluid, while filling both may
provide a third flow rate. Depending upon the particular conditions of
the patient (e.g.--the patient's current level of pain), the medical
professional may determine what chambers to fill and/or leave empty. In
combination with the aforementioned direct bolus injection capability,
this three flow design is clearly beneficial to both a patient and
medical professional. As pump 10 is designed to house a limited amount of
medication fluid, it must be refilled regularly. A doctor or nurse may
utilize the regularly scheduled replenishment procedure as an opportunity
to further monitor the patient and determine the proper flow rate for
treating the patient's infirmity. Thus, if a doctor determines that the
patient requires more medication fluid to be directed to the afflicted
area, he/she may simply fill both chambers, or the single chamber
associated with the faster flow rate resistor. Alternatively, when less
medication is desired, only one chamber or the chamber associated with
the slower resistor may be filled. While allowing multiple flow rates,
the design of the present dual reservoir constant flow pump 10 is an
improvement upon complicated programmable pumps, as the present invention
merely requires simple injections, or lack there of, to refill the
correct chambers, rather than the operation of complicated mechanisms or
electronics. As is clearly recognized by those of ordinary skill in the
art, these replenishing injections are something that are required in the
proper operation of all pumps, regardless of their type.

[0033] In addition to the varying flow rate discussed above, the design of
pump 10 also allows for the administration of up to two different active
substances, or a combination of both, from a single pump. Clearly, the
dual reservoir design of pump 10 as shown in FIGS. 1 and 2 may allow for
two different medication fluids or the like to be housed in chambers 14
and 16. Thereafter, upon the expansion of a propellant housed within
chamber 18, either one or both (depending on which chambers have been
filled) may be administered to a patient.

[0034] As the various ports 24, 30 and 36 of pump 10 (as well as their
respective septa 26, 32, 38) are located to the side, and are not located
above chambers 14, 16 and 18, housing 12 is of low profile and may be
comprised of only the aforementioned top and bottom portions 12a and 12b
simply affixed together by any well known means, such as adhesive,
welding, screw cooperation, snap fitting and the like. Top and bottom
portions 12a and 12b preferably cooperate so as to capture and retain
membranes 20 and therebetween. As shown in FIG. 1 and the more detailed
exploded view of FIG. 3, top and bottom portions 12a and 12b preferably
form an attachment area 54 for achieving this capturing and retaining of
the membranes. Attachment area 54 preferably includes a projection 56
located bottom portion 12b and a depression 58 located on top portion
12a. During assembly, top and bottom portions 12a and 12b are sandwiched
together, with membranes 20 and 22 therebetween. This sandwiching step
necessarily causes projection 56 to be forced into depression 58.
Similarly, a portion of each membrane 20 and 22 is also forced into
depression 58 by projection 56. Thus, a crimp-like connection is formed,
thereby capturing and retaining membranes 20 and 22 between top and
bottom portions 12a and 12b. It is noted that other configurations for
attachment area 54 are envisioned, as would be apparent to those of
ordinary skill in the art.

[0035] In accordance with the present invention, another embodiment
implantable pump 110 is depicted in FIGS. 4-6. It is noted that pump 110
operates in a similar fashion to that of the above described pump 10. As
such, like elements of pump 110 are labeled with similar reference
numerals, but within the 100 series of numbers. For example, the two
membranes of pump 110 are similar to the above described membranes 20 and
22, and as such, are labeled as 120 and 122. Rather than being a pump
with the above described three constant flow rate capability, pump 110 is
designed to be a constant flow rate pump with patient controlled
actuation capabilities. Essentially, chamber 114 is utilized to provide a
constant flow of fluid to catheter 136, in substantially the same manner
as described above with regard to chamber 14 of pump 10. However, in this
second embodiment, chamber 116 is utilized for providing fluid to a
patient controlled actuation assembly, which will be discussed more fully
below.

[0036] As briefly mentioned above, fluid expelled from chamber 114 passes
through a constant flow resistor 138, through bolus port 146, to catheter
136. This is similar to the above discussed operation of chamber 14 of
pump 10, and is shown in both FIGS. 4 and 6. In this embodiment however,
fluid housed within chamber 116 passes through channels 184a and 184b to
an electronic patient controlled actuation unit 170 capable of allowing
for patient controlled bolus doses to be administered in a manner to be
further described. Unit 170 includes an electronic unit 171, and a valve
assembly 172 having a first cylinder 174 and a second cylinder 176, which
will be discussed further below in connection with FIGS. 7-10. Finally,
in a similar fashion to bolus port 46 of pump 10, pump 110 also includes
a bolus port 146 for allowing direct access to catheter 136.

[0037] Valve assembly 172 is more particularly shown in the enlarged and
more detailed views of FIGS. 5-10. As noted above, assembly 172 comprises
a first cylinder 174 and a second cylinder 176, which house first and
second pistons 178 and 180 respectively. First piston 178 further
includes five piston sections 178a, 178b, 178c, 178d and 178e separated
by four o-rings 179a, 179b, 179c and 179d. As depicted in FIGS. 7-10,
piston sections 178a and 178e are adapted to be attracted by electrical
forces or the like. For example, piston sections 178a and 178e may be a
metallic material that may be attracted by magnets or coils 182a and 182b
encompassing the ends of first cylinder 174. Piston sections 178b, 178c
and 178d are dimensioned so as to have an outside diameter which are
smaller than the inside diameter of first cylinder 174. Thus, fluid may
pass through a channel or circular opening formed between the piston
sections and the cylinder. The aforementioned o-rings 179a-d define these
piston sections and also seal the channels or openings formed by each
section and first cylinder 174 from each other. In a similar fashion,
piston 180 includes two o-rings 181a and 181b for sealing the piston
against second cylinder 176. However, it is noted that piston 180 is
sized so as to fit more snuggly within second cylinder 176, and is not
adapted to form useful channels or openings therebetween.

[0038] Valve assembly 172 further includes two openings 173a and 173b for
receiving the aforementioned inlets 184a and 184b in fluid communication
with chamber 116, a single outlet 186 in fluid communication with bolus
port 146 and catheter 136, and two passages 188a and 188b that allow
first cylinder 174 and second cylinder 176 to be in fluid communication.
It is noted that the cross sectional bottom view of FIG. 5 more
particularly shows the fluid communication between chamber 116 and valve
assembly 172. As shown in that figure, inlets 184a and 184b essentially
extend between each of those components. However, in other embodiments, a
single exit from chamber 116 may be connected to openings 173a and 173b
of valve assembly 172 by a Y-joint or the like. As more clearly shown in
the side view of FIG. 6, outlet 186 extends between first cylinder 174
and bolus port 146. This ultimately allows for fluid dispelled from valve
assembly 172 to exit through catheter 136. It is noted that outlet 186
extends in a direction which is perpendicular to inlets 184a and 184b.
This is depicted in FIGS. 5 and 6, by showing the ends of these
components. However, with regard to FIGS. 7-10, these components are
shown in a parallel relationship for clarity purposes. Finally, as best
shown in FIG. 6, bolus port 146 may include a plate 190 for preventing
the inadvertent access of outlet 186 by a needle inserted into port 146.

[0039] The operation of valve assembly 172 will now be discussed in
conjunction with FIGS. 7-10, which depict the sequence of movements of
the various components of the valve assembly. Initially, pistons 178 and
180 are located in the positions depicted in FIG. 7. It is noted that in
this position, fluid is located in the empty portion of cylinder 176
located to the left of piston 180. However, because of the cooperation of
the other elements of assembly 172, no fluid is capable of being
dispelled. Most notably, passage 188b is not in fluid communication with
inlet 184a, and passage 188a is not in fluid communication with outlet
186. However, upon the activation of magnet 182a by the patient, section
178a of first cylinder 178 is pulled towards magnet 182a, resulting in
the position shown in FIG. 8.

[0040] Subsequent to the movement of first cylinder 178, as shown in FIG.
8, inlet 184a is now in fluid communication with passage 188a, as the
position of piston 178 allows for fluid to pass around piston section
178d. Thus, fluid being constantly expelled from chamber 116 is capable
of flowing through inlet 184a and around piston section 178d, through
passage 188a, to a position within second cylinder 176 to the right of
piston 180. Upon the build up of sufficient pressure (provided by the
constant flow from chamber 116), piston 180 is displaced within second
cylinder 176 in the direction depicted by arrow X. This, in turn, pushes
the fluid contained to the left of piston 180 through passage 188b,
around piston section 178c, through outlet 186 and eventually through
catheter 136 to a portion of the body of the patient in which pump 110 is
implanted. Therefore, a predetermined amount of fluid is expelled from
pump 110, while a substantially similar amount of fluid remains to the
right of the recently displaced piston 180. This latter position is shown
in FIG. 9.

[0041] With piston 180 now being situated to the left side of second
cylinder 176 and fluid located within second cylinder 176 to the right
side of piston 180 (as shown in FIG. 9), piston 178 may now be moved
within first cylinder 174 in the direction of arrow Y, shown in FIG. 9.
Once again, it is noted that this may be accomplished by activating
magnet 182b. FIG. 10 depicts the position of piston 178 within first
cylinder 174 after the activation of magnet 182b. This right side
position now creates an open fluid passage extending through inlet 184b,
around piston section 178b, through passage 188b and into second cylinder
176 to the left of piston 180. Similarly, an open fluid passage now
exists from the right side of piston 180 within second cylinder 176,
through passage 188a, around piston section 178c, and through outlet 186,
where it may ultimately exit catheter 136. Like that described above,
fluid being expelled from chamber 116 displaces piston 180 to the right,
thereby expelling the fluid contained within second cylinder 176. Thus, a
predetermined amount is injected into the patient's body and a similar
amount is recharged into second cylinder 176 on the opposite side of
piston 180. Upon completion of this step, the components of valve
assembly 172 retain the position depicted in FIG. 7. Thus, the above
described steps may be followed to perform more patient desired
injections.

[0042] This patient actuated process may be conducted over and over again
through the selective actuation of magnets or coils 182a and 182b. The
only limitation to the amount of times the process may be performed is
the overall amount of fluid housed within chamber 116. It is noted that
actuation of magnets 182a and 182b may be accomplished through many
different procedures. For example, as mentioned above, unit 170 includes
an electronic unit 171 which preferably has a power source, such as a
battery. This power source preferably may be selectively applied to
either magnet 182a or 182b. In a simplistic form, magnets 182a and 182b
may be connected to the power source through a well known electrical
connection and a switch may be employed for choosing which magnet gets an
electrical current applied thereto.

[0043] Further, a controlling mechanism is preferably provided for
selectively applying power to the magnets. Many different such mechanisms
are well known and widely utilized with implantable devices for
implantation into a patient's body. For example, prior art devices have
shown that it is possible to utilize dedicated hard wired controllers,
infrared controllers, or the like, which controllers could be used in
accordance with the present invention to control various elements. U.S.
Pat. No. 6,589,205 ("the '205 patent"), the disclosure of which is hereby
incorporated by reference herein, teaches the use of a wireless external
control. As discussed in the '205 patent, such a wireless control signal
may be provided through modulation of an RF power signal that is
inductively linked with the pump. The '205 patent cites and incorporates
by reference U.S. Pat. No. 5,876,425, the disclosure of which is also
hereby incorporated by reference herein, to teach one such use of forward
telemetry or the exchange of information and programming instructions
that can be used with the present invention to control the pump and the
various aforementioned elements that are varied in order to affect the
flow rate. However, it is noted that similar external controllers may
also be utilized. Such controllers can send control signals wirelessly
(such as by IR, RF or other frequencies) or can be wired to leads that
are near or on the surface of the patient's skin for sending control
signals. Furthermore, a pump in accordance with the present invention may
include safeguards to prevent the inadvertent signaling or improper
programming of the pump. For example, the present invention could utilize
a secure preamble code or encrypted signals that will be checked by
software or hardware used for controlling the pump or even dedicated only
for security purposes. This preamble code would prevent the inadvertent
actuation of magnets 182a and 182b, from being caused by outside
unrelated remote control devices or signals and by other similar pump
controllers.

[0044] Preferably, an additional controller may be provided to prevent a
patient from over utilizing the patient controlled actuation features.
Preferably, such controller may include a digital timer (i.e. a clock)
that must time out (after a pre-selected interval of time before the
patient can actuate the magnets again. Other safety precautions may be
used, such as passwords, hardware or software keys, encryption, multiple
confirmation requests or sequences, etc. by the software or hardware used
in the programming of the pump to prevent over-use of the patient
controlled dose.

[0045] The electronics and control logic used with the present invention
for control of the magnets may be located internally with or in the
implantable pump and/or externally with any external programmer device
used to transmit pump programming information to control the pump. The
electronics can also be used to perform various tests, checks of status,
and even store information about the operation of the pump or other
physiological information sensed by various transducers.

[0046] An external programmer device may also be avoided by incorporating
the necessary logic and electronics in or near or in the implantable pump
such that control can be accomplished, for example, via control buttons
or switches or the like that can be disposed on or below the surface of
the skin. Of course, necessary precautions (such as confirmation button
pressing routines) would need to be taken so that inadvertent changing of
programming is again avoided.

[0047] Although the invention herein has been described with reference to
particular embodiments, it is to be understood that these embodiments are
merely illustrative of the principles and applications of the present
invention. It is therefore to be understood that numerous modifications
may be made to the illustrative embodiments and that other arrangements
may be devised without departing from the spirit and scope of the present
invention as defined by the appended claims.